Spark plug with gas insulation for internal combustion engines



Dec. 19, 1961 LAGYI 3,014,150

I. SZl

SPARK PLUG WITH GAS INSULATION FOR INTERNAL COMBUSTION ENGINES Filed Aug. 14, 1957 Fig.1

IN V EN TOR.

Fig.4

AIM/I J 'G Agar/r United States Patent @tifiee 3,014,15d Patented Dec. 19, 1961 3,014,150 SPARK PLUG WITH GAS lNdULATliON FOR INTERNAL COMBUSTHUN ENGINE Istvan Szilgyi, Budapest, Hungary, assignor to Licencia Talalmanyokat Ertekesito Vallalat, Budapest, Hungary Filed Aug. 14, .1957, Ser. No. 678,199 5 Claims. (Cl. 313--129) The invention relates to spark plugs for internal combustion engines. More in particular the invention concerns spark plugs of the type having a central electrode surrounded by a tubular insulating body in a manner that an annular space is defined between the electrode and the tubular body or tube.

In prior art devices of this type the annular space is in operation connected with the combustion chamber of a motor cylinder with which the spark plug is associated. Thus, if the tube is made of glass or of other transparent material it is readily possible to observe the course of the ignition and explosion, an advantage in the maintenance and operation of the engine. With such an arrangement the gas can penetrate from the engine cylinder into the tube or between the tube and the center electrode. This arrangement is advantageous even Where the tube is not made of transparent material where no opportunity is provided to permit the convenient observation of the course of the ignition and explosion. In such an arrangement the gas entering into the space between the tube and the electrode reliably aids in avoiding current break down because the insulation effect of the gas under pressure is very high.

Spark plugs of this type in accordance with the prior art have the shortcoming that the insulating tubes which surround the center electrode break frequently. This breakage is caused by the difierence in the expansion caused by heat but it has not been possible to overcome it even if the coefiicients of expansion of the metal and of the glass are substantially the same. On the one hand the heating of the individual components, especially if a cold engine is started involves diflerent time factors, while on the other hand the form and dimensions of the components of the spark plug diflfer specifically and from each other. Also, in operation, high temperatures are devel oped which may cause the tube to expand considerably more than the metal and thus result in breakage.

In accordance with the invention it has also been found that contrary to previous wide spread general beliefs the individual components of the spark plugs can be secured by elastic pressures. It was the general concept that in the construction of spark plugs only rigid connections could be used so that it was not recognized that it would be possible to secure the tube surrounding the center electrode for reliable operation also by inserting a spring.

It is an object of the present invention to eliminate the foregoing shortcomings and as primary object the invention provides for elastically mounting the tube surrounding the center electrode or to retain it in place under elastic pressure. p

Mounting the tube under elastic pressureor under bias has been found to eliminate the breakage as well as leakage at the juncture between the tube spark plug."

It has also been discovered that placing the tube under pressure provides the surprising result that the resistance of the insulation tube against central pressure is increased in the presence of high temperatures and if pressures are' and the body of the.

applied to the tube from both ends and it is then subjected to a load it resists the strains from the hot gases butter than if no pressure is applied.

It is, therefore, an additional object ofthe invention to strengthen the tube surrounding the electrode of the spark plug by placing it under pressure from its ends, thereby improving the qualities of the material for the intended purpose.

Thus the invention provides a spark plug for internal combustion engines in which the one electrode is disposed centrally in the form of a rod and surrounded by a tube in such a manner that between the central electrode and the tube a space is formed which can be penetrated by the gases from the cylinder of the engine with which it is associated, which tube is mounted in such a manner that it can expand in axial direction to prevent breaks while avoiding leaks and which is under pressure by spring bias axially to increase its resistance against strains.

Further details and objects of the invention will become apparent from the following description of the several embodiments of the invention illustrated in the accompanying drawings in which FIG. 1 is a longitudinal cross section of one embodiment of a spark plug in accordance with the invention,

FIG. 2 is a partial sectional view of another embodiment of the invention,

FIG. 3 is a partial elevational view of ment of the invention, and

FIG. 4 illustrates a portion of a fourth embodiment in partial cross section.

Similar reference numerals in the drawings refer to similar components.

FIG. 1 shows the center electrode 1, the body electrode 2, the threaded portion for mounting the spark plug, and the insulating tube 4 may suitably be made of transparent material such as quartz-glass and formed cylindrically, as shown, or of conical shape. The body or housing 5 of the spark plug defines a shoulder 5a at its lower end: against which the tube 4 is supported with a gasket or sealing ring 4a or cementing material placed therebetween.

a third embodithe tube 4 with a gasket or sealing ring 4b or cement material placed between the head and the tube. In the embodiment shown the electrode 1 is pressed into a borein the head la. A pin 7 provided with a collar firmly presses down on the head la under the pressure of a spring 6 the upper end of which rests against a shoulder or insert 8 of insulating material which threadedly en gages the housing 5 ofthe spark plug. 'The upper extension 7a of the pin 7 t can be utilized as a contact for supplying current.

FIG. 1 clearly indicates the manner in which the center electrode is secured by an elastic bias. Spring 6 and pin 7 retain electrode l as well as the tube or sleeve 4 in their electrode 1 and tube 4 exert a tension' force upon the tube over its entire length-which force is equal in radial The center electrode 1 is provided with an enlarged upper portion or head 1a which holds down to but what I desire to protect by Letters Patent directions. Consequently the tube has no tendency to shift longitudinally so that in operation the spring 6 is subjected only to that force which the gases exert upon the annular surface 112 of the head la between tube 4 and electrode 1. Since, however, this annular surface is very small the upwardly directed force is of small value so that the load on spring 6 which is the tension imparted during assembly changes only to a small extent.

The tube 4 is suitably pressed down by spring 6 under all conditions so that the very small changes in length of the tube may take place without breakage and danger of leakage. This arrangement also permits of forming the spark plug with a lower extension 3 of suitable length so that thespark gap is located atthe proper place and the spark plug ignites in the advantageous location of the explosion space.

It is possible to observe the insulating tube 4 through two windows of relatively large size defined in the body of the spark plug 5. One of the two windows is shown in KG. 1 at 5b.

In principle the effect of the construction of the embodiment of FIG. 2 is the same as of that in accordance with FIG. 1, however the manner of pressing down the insulating tube or of obtaining the fastening pressure is different. The head member la of the electrode is not pressed down by a helical spring as in FIG. 1, but by a cup shaped spring 6a which rests against the lower surface of member 8a. The current supply rod 7a is secured in the head member 1a.

In the embodiment in accordance with FIG. 3 a head 1c is shown which is inherently elastic for which purpose the head is formed with slots which extend alternately from the left and from the right into the head.

In the embodiment of FIG. 4 the annular space, which accommodates the helical spring 6 in the embodiment of FIG. 1, receives a rigid support 9 of heat insulating material and a resilient member 10 of elastic plastic material. Thus, in this embodiment the helical spring 6 is replaced by the annular elastic member 10.

7 It has been established by tests that the current has a tendency to break through between head portion 1a and the body of the spark plug 5 if high electrical potentials are used. To avoid this the inner surface of the spark plug which faces the center electrode is provided in accordance with the invention with a thin insulating layer, for example of varnish or enamel or with an insulation insert placed through window 5b as shown at 11 in FIG. 1. It has been found that this reliably prevents break through.

Having now, described my invention with reference to the embodiments'shown I do not wish to be limited thereis set forth in the appended claims.

I claim: p I 7 ,l. A spark plug for internal combustion engines comprising a body or housing, a generally rod shaped center electrode extending in the lower end of said housing and protruding therefrom, a body electrode proximate the protruding end of said center electrode, a tube of insulating material disposed about said center electrode defining aspace between said electrode and said tube open at the lower end thereof adapted to communicate with the motor chamber, and elastic means disposed endwise of said tube adjacent the other end of said electrode and biasing said tube toward the bottom end of said spark plug and downwardly in the axial direction of said protruding end axial expansion and contraction of said tube while sealing the space around the upper end of said electrode and preventing breakage and leakage, and a head member intermediate said elastic means and said tube biased of said electrode and permitting against said tube and supporting said center electrode within said tube,

2. A spark plug for internal combustion engines coma generally rod-shaped center lowerend oisaid housing and prising a body or housing, electrode extending in the protruding therefrom,

protruding therefrom, a body electrode proximate the protruding end of said center electrode, a tube of insulating material disposed about said center electrode defining a space between said electrode and said tube open at the lower end thereof adapted to communicate with the motor chamber, and elastic means disposed endwise of said tube adjacent the other end of said electrode and biasing said tube toward the bottom end of said spark plug and downwardly in the axial direction of said protruding end of said electrode and permitting axial expansion and contraction of said tube while sealing the space around the upper end of said electrode and preventing breakage and leakage, and a head member intermediate said elastic means and said tube biased against said tube and supporting said center electrode within said tube, the lower end of said body presenting a shoulder against which one end of said tube is biased, said elastic means being mounted in an insulating member secured in the housing of said spark plug and a gasket between said one end of said tube and said shoulder and between the other end of said tube and said head member.

3. A spark plug for internal combustion engines comprising a body or housing, a generally rod shaped center electrode extending in the lower end of said housing and protruding therefrom, a body electrode proximate the protruding end of said insulating material disposed about said center electrode defining a space between said electrode and said tube open at wise of said tube adjacent the other end of said electrode and biasing said tube toward the bottom end of said spark plug and downwardly in the axial direction of said protruding end of said electrode and permitting axial expansion and contraction of said tube while sealing the space around the upper end of said electrode and preventing breakage and leakage, and a head member intermediate said elastic means and said tube biased against said tube and supporting said center electrode within said tube, said elastic means including a pin having a collar and having one end in engagement with said head memher and another end for contact with a supply of potential.

4. A spark plug for internal combustion engines com prising a body or housing, a generally rod shaped center electrode extending in the lower end of said housing and a body electrode proximate the protruding end of said center electrode, a tube of insulating material disposed about said center electrode defining a space between said electrode and said tube open at the lower end-thereof adapted. to communicate with the motor chamber, and elastic means disposed endwise of said tube adjacent the other end of said electrode and biasing said tube toward the bottom end of said spark plug and downwardly in the axial direction of said protruding end of said electrode and permitting axial expansion and.

contraction of said tube while sealing the space around the upper end of said electrode and preventing breakage and leakage, and a head member intermediate said elastic means and said tube biased against said tube and supporting said center electrode within said tube, said elastic means including a pin having one end in engagement with said head member and another end for contact with a supply' of potential and a pair of cup shaped spring elements disposed about said pin.

5. A spark plug for internal combustion engines com-- tor chamber, and'elastic means disposed endwise of said tube adjacent the other end of said electrode and biasing said tubetoward the bottom end of said spark plug and downwardly inthe axial direction'of said protruding endcenter electrode, a tube of the lower end thereof adapted to communicate. with the motor chamber, and elastic means disposed end a body electrode proximate the 5 of said electrode and permitting axial expansion and contraction of said tube While sealing the space around the upper end of said electrode and preventing breakage and leakage, and an insulation layer inside said housing around said tube and said center electrode.

References Cited in the fiie of this patent UNITED STATES PATENTS 1,110,813 Noble Sept. 15, 1914 6 Ryder Jan. 10, 1922 Vila Nov. 1, 1938 Kasarjian Feb. 4, 1947 FOREIGN PATENTS France July 8', 1914 Great Britain Oct. 26, 1922 

